Akiyuki Hamasaki

One-Pot Synthesis of Indoles and Aniline Derivatives from Nitroarenes under Hydrogenation Condition with Supported Gold Nanoparticles

One-pot sequences of hydrogenation/hydroamination to form indoles from (2-nitroaryl)alkynes and hydrogenation/reductive amination to form aniline derivatives from nitroarenes and aldehydes were catalyzed by Au nanoparticles supported on Fe(2)O(3). Nitro group selective hydrogenations and successive reactions were efficiently catalyzed under the conditions.

Enhancement of reaction efficiency by functionalized alcohols on gold(I)-catalyzed intermolecular hydroalkoxylation of unactivated olefins.

Intermolecular hydroalkoxylation of unactivated olefins catalyzed by the combination of gold(I) and electron deficient phosphine ligands has been developed. Although pairings of unactivated olefins and common aliphatic alcohols gave unsatisfactory results in gold catalyzed hydroalkoxylations, the use of alcohol substrates bearing coordination functionalities such as halogen or alkoxy groups showed great improvement of reactivity.

Hydrolytic enantioselective protonation of cyclic dienyl esters and a β-diketone with chiral phase-transfer catalysts

Hydrolytic enantioselective protonation of dienyl esters and a β-diketone catalyzed by phase-transfer catalysts are described. The latter reaction is the first example of an enantio-convergent retro-Claisen condensation. Corresponding various optically active α,β-unsaturated ketones having tertiary chiral centers adjacent to carbonyl groups were obtained in good to excellent yields and enantiomeric ratios (83-99%, up to 97.5:2.5 er).

Aerobic oxidation of cyclohexanones to phenols and aryl ethers over supported Pd catalysts

Transformation of cyclohexanones to phenols and aryl ethers over supported Pd catalysts using molecular oxygen as the sole oxidant is developed. Several metal oxide supported Pd catalysts were used to activate the C–H bond in cyclohexanones to produce cyclohexenones and phenols through oxidation. Although the selectivity of cyclohexenones was difficult to control, phenols were obtained in excellent yield with a broad substrate scope. A novel catalytic system, using ZrO2 supported Pd(OH)2, was proposed for the synthesis of aryl ethers, and the products were obtained in moderate to excellent yields. Orthoesters, such as trimethyl orthoformate (TMOF), triethyl orthoformate (TEOF), and triisopropyl orthoformate (TIPOF), enabled nucleophilic addition and elimination after activation of cyclohexanones over a Pd catalyst to produce the corresponding aryl ethers. TIPOF was also used as the dehydrating reagent to promote the reaction of cyclohexanones with alcohols for the preparation of versatile aryl ethers.

Homogeneous Pd-Catalyzed Transformation of Terminal Alkenes into Primary Allylic Alcohols and Derivatives

Synthesis of primary alcohols from terminal alkenes is an important process in both bulk and fine chemical syntheses. Herein, a homogeneous Pd-complex-catalyzed transformation of terminal alkenes into primary allylic alcohols, by using 5 mol % [Pd(PPh3)4] as a catalyst, and H2O, CO2, and quinone derivatives as reagents, is reported. When alcohols were used instead of H2O, allylic ethers were obtained. A proposed mechanism includes the addition of oxygen nucleophiles at the less-hindered terminal position of π-allyl Pd intermediates.

Gold nanoparticles assisted formation of cobalt species for intermolecular hydroaminomethylation and intramolecular cyclocarbonylation of olefins

The intermolecular hydroaminomethylation and the intramolecular cyclocarbonylation efficiently proceeded on cobalt oxide supported gold nanoparticles. The intermolecular reaction employing terminal olefins and N-isopropylaniline afforded hydroaminomethylated products as a mixture of regioisomers via a common reaction path consisting of hydroformylation, imine formation, and hydrogenation. In contrast, indolinone derivatives were exclusively obtained in the case of 2-alkenylanilines based on the intramolecular cyclocarbonylation mechanism. Both of these reactions were catalyzed by cobalt species derived from cobalt oxide. The active cobalt species were formed via reduction of the oxide support promoted by deposited gold nanoparticles. Characterization of the catalysts before and after the reaction was also performed.

Efficient Decarbonylation of Furfural to Furan Catalyzed by Zirconia‐Supported Palladium Clusters with Low Atomicity

Decarbonylation of furfural to furan was efficiently catalyzed by ZrO2 -supported Pd clusters in the liquid phase under a N2 atmosphere without additives. Although Pd/C and Pd/Al2 O3 have frequently been used for decarbonylation, Pd/ZrO2 exhibited superior catalytic performance compared with these conventional catalysts. Transmission electron microscopy and X-ray absorption fine structure measurements revealed that the size of the Pd particles decreased with an increase in the specific surface area of ZrO2 . ZrO2 with a high surface area immobilized Pd as clusters consisting of several (three to five) Pd atoms, whereas Pd aggregated to form nanoparticles on other supports such as carbon and Al2 O3 despite their high surface areas. The catalytic activity of Pd/ZrO2 was enhanced with a decrease in particle size, and the smallest Pd/ZrO2 was the most active catalyst for decarbonylation. When CeO2 was used as the support, a decrease in Pd particle size with an increase in surface area was also observed. Single Pd atoms were deposited on CeO2 with a high surface area, with a strong interaction through the formation of a Pd-O-Ce bond, which led to a lower catalytic activity than that of Pd/ZrO2 . This result suggests that zero-valent small Pd clusters consisting of more than one Pd atom are the active species for the decarbonylation reaction. Recycling tests proved that Pd/ZrO2 maintained its catalytic activity until its sixth use.